Watt withdrew from the firm in 1800, on the expiry of his patent for the condensing steam-engine; but Boulton continued until the year 1809, when he died full of years and honours. Watt lived on until 1819. The last part of his life was the happiest. During the time that he was in the throes of his invention, he was very miserable, weighed down with dyspepsia and sick headaches. But after his patent had expired, he was able to retire with a moderate fortune, and began to enjoy life. Before, he had "cursed his inventions," now he could bless them. He was able to survey them, and find out what was right and what was wrong. He used his head and his hands in his private workshop, and found many means of employing both pleasantly. Murdock continued to be his fast friend, and they spent many agreeable hours together. They made experiments and devised improvements in machines. Watt wished to make things more simple. He said to Murdock, "it is a great thing to know what to do without. We must have a book of blots--things to be scratched out." One of the most interesting schemes of Watt towards the end of his life was the contrivance of a sculpture-making machine; and he proceeded so far with it as to to able to present copies of busts to his friends as "the productions of a young artist just entering his eighty-third year." The machine, however, remained unfinished at his death, and the remarkable fact is that it was Watt's only unfinished work. The principle of the machine was to carry a guide-point at one side over the bust or alto-relievo to be copied, and at the other side to carry a corresponding cutting-tool or drill over the alabaster, ivory, jet, or plaster of Paris to be executed. The machine worked, as it were, with two hands, the one feeling the pattern, the other cutting the material into the required form. Many new alterations were necessary for carrying out this ingenious apparatus, and Murdock was always at hand to give his old friend and master his best assistance. We have seen many original letters from Watt to Murdock, asking for counsel and help. In one of these, written in 1808, Watt says: "I have revived an idea which, if it answers, will supersede the frame and upright spindle of the reducing machine, but more of this when we meet. Meanwhile it will be proper to adhere to the frame, etc., at present, until we see how the other alterations answer." In another he says: "I have done a Cicero without any plaits--the different segments meeting exactly. The fitting the drills into the spindle by a taper of 1 in 6 will do. They are perfectly stiff and will not unscrew easily. Four guide-pullies answer, but there must be a pair for the other end, and to work with a single hand, for the returning part is always cut upon some part or other of the frame."